you are only going to get 1x speed since you only have a PCI-E x1 slot. You are going to be WAY overspending for the card you will get. Why pay $90 for an outdated video card when you can upgrade your Motherboard and GPU for a little more $.

Best option is the 5450 PCI-E x1 version but any PCI-E x 1 will work on your current setup.